C / C++ / MFC

3-Nov-02 13:55

Hello I'd like to declare a char* that points to a void* but i dont know the best way to do this, I thought i could use type casting but it appears not.
I'm trying to use strcmp to compare 2 char* pointing to buffers the code is this...

void * __cdecl buffer= malloc(100);<br />
void * __cdecl buffer2 = malloc (100);<br />
__int64 filel1 =_filelengthi64( firstfiledone);<br />
__int64 filel2 =_filelengthi64( firstfiledtwo);<br />
if (filel1!=filel2)<br />
        return 1;<br />
char* b,b2;<br />
int trys1=filel1/100,count;<br />
for (count=0;count<filel1;count=count+trys1)<br />
	{<br />
	fread( buffer, 1, 100, s1 );<br />
	fread( buffer2, 1, 100, s2 );<br />
	b= (char*) static_cast <char*> (void * __cdecl) buffer;<br />
	b2= (char*) static_cast <char*> (void * __cdecl) buffer2;<br />
	if ((strcmp (b,b2))==0)<br />
		{<br />
		printf ("ok");<br />
		}<br />
        }

But that way doesnt work so is there any way of easily doing this?
Also what is a volatile pointer. As i've previously copied a supposedly volatile pointer bit by bit, then re-used it later with no bad effects, is this method sloppy code?

Thanks hope you can help ! - Jason Poke tongue | ;-P

ps tried to get rid of them errors in the code with the boolean expression things dont know if it worked

Nick Parker3-Nov-02 15:51

Nick Parker

3-Nov-02 15:51

Jay2 wrote:
I'm trying to use strcmp to compare 2 char* pointing to buffers the code is this...

Not sure that this will fix things, however you need to check your declaration of your two character pointers. It should look something like this( you have char* b,b2;):

char *b, *2;

Jay2 wrote:
Also what is a volatile pointer

Here is a link to save space. Data Type Qualifiers[^]

Hope this helps. Smile | :)

Nick Parker

May your glass be ever full.
May the roof over your head be always strong.
And may you be in heaven half an hour before the devil knows you’re dead. - Irish Blessing

ian mariano3-Nov-02 15:57

ian mariano

3-Nov-02 15:57

Wow, you really have to work on formatting your code a little bit.

Your casts are odd as well and you'll have problems because strcmp expects strings to be NULL (0) terminated, you are better off using strncmp so you can set a max comparison size (in your case 100.) Also, what happens if fread reads less than 100 bytes or past the end of a either file? MSDN states "The file-pointer position is indeterminate if an error occurs. The value of a partially read item cannot be determined."

If you malloc you better free! You allocate memory, but then you do a return without ever freeing the memory, you also return without ever _closeing the file handles (or is this done somewhere else?)

Do you really need to use a void pointer? Take a look at the following example on MSDN: fread()[^]

If you just use a buffer of char, you should be on your way.

You should also check for end of files (using feof), and read errors (fread returning 0). Error handling is extremely important, and should never never never ever be omitted for production code (ever.) For illustrative purposes, many people do omit error handling, usually with a caveat that they've done so, or that the lack thereof is implied Cool | :cool:

Hopefully this will help you on your way.

"The greatest danger to humanity is humanity without an open mind."
- Ian Mariano - http://www.ian-space.com/

Jay24-Nov-02 5:46

4-Nov-02 5:46

Hi, I know the casts are odd! I couldnt think of any other way of thinking about it... not sure even if it is the correct cast but as a char* and void* are stored in memory (I think) the same way then I decided it would be possible.

I have to use a void* for fread to read from the file into the buffer which is void*, I think your strncmp looks like what i need to use but will this still assume there is a NULL character to terminate the string?

Incase that doesnt work maybe i can use sprintf to write from the buffer into a string, but i never like doing that kind of thing as i'm not really a fan of sprintf, and as the buffer is in binary i'm not even sure if it will work fully, is there no way of comparing 2 buffers or arreas of allocated memory, how about taking one from the other and seeing if the result is zero as this would save me a lot of messing around!

Ok thanks the code i showed you was only a small section of the program and i have closed the files, but not free'd the allocate memory yet.
Oh is that link the one used in msdn v6.0 i know as thats the version i have it's old but thats all i have, and when i click the link i dont get anything at all!

Thanks i'll have a play around with msdn.. - Jason

ian mariano4-Nov-02 6:54

ian mariano

4-Nov-02 6:54

strncmp doesn't require a NULL terminator. fread will accept char pointers for the buffer as well.

"The greatest danger to humanity is humanity without an open mind."
- Ian Mariano - http://www.ian-space.com/

Jay24-Nov-02 5:57

4-Nov-02 5:57

sorry to spam your email like this... i think fscanf is the thing to use.;P

Christian Graus3-Nov-02 16:38

3-Nov-02 16:38

Why do you need to do things this way ? Are you using C rather than C++ ?

Christian

No offense, but I don't really want to encourage the creation of another VB developer. - Larry Antram 22 Oct 2002

Hey, at least Logo had, at it's inception, a mechanical turtle. VB has always lacked even that... - Shog9 04-09-2002

During last 10 years, with invention of VB and similar programming environments, every ill-educated moron became able to develop software. - Alex E. - 12-Sept-2002

Jay24-Nov-02 5:27

4-Nov-02 5:27

Hi no i'm not using c, using c++ but for console applications, i'm comparing 2 different system files (actually i'm backing up windows installing some bits and pieces then comparing the new files with the backed up copies).

Christian Graus4-Nov-02 11:28

How to fully override a pop-up menu item?

4-Nov-02 11:28

If you're using C++, you should use C++. Use new and delete instead of malloc and free, iostreams instead of fread. You'll find that the iostreams in particular greatly simplify what you're trying to do, and your code will be a lot nicer to read, also.

Christian

No offense, but I don't really want to encourage the creation of another VB developer. - Larry Antram 22 Oct 2002

Hey, at least Logo had, at it's inception, a mechanical turtle. VB has always lacked even that... - Shog9 04-09-2002

During last 10 years, with invention of VB and similar programming environments, every ill-educated moron became able to develop software. - Alex E. - 12-Sept-2002

3-Nov-02 13:26

Each pop-up menu item has an arrow on the right, even when we override the menu item to be ownerdrawn. Windows seems to pull drawing for the right pointing triangle outside drawing context for pop-up menu items Frown | :(

Does anybody know how to override this windows restriction and yet draw the triangle ourselves Confused | :confused:

Regards,
Vitaly

P.S. None of the articles about menus on this website has such feature as i could see.

Windows 98 Problems

Swinefeaster3-Nov-02 11:15

3-Nov-02 11:15

Hi guys,

I'm developing an app and having a complete nightmare trying to support Windows 98! It runs solid like a rock on Windows 2000 and Xp, but with 98 it just crashes in the oddest of places. One of these is inside the AlphaBlend() function, which is a new function included in the November 2001 Platform Sdk. It is supposed to work under 98 no problem. Frown | :(

The AlphaBlend() code crashes inside msimg32.dll, and I read somewhere that you must not package this dll with your product... I am currently not doing this, but wonder if perhaps I should anyway ?

Does anyone have any ideas what could be going wrong? I'm debating just adding fine print saying something like "Run on Windows 98 at your own risk" Cry | :((

swinefeaster

Check out Aephid Photokeeper, the powerful digital
photo album solution at www.aephid.com.

Swinefeaster3-Nov-02 21:55

3-Nov-02 21:55

Thanks! It's good to know the version numbers... Perhaps I'll combine that with Christian's code and together it might just be a fix Smile | :)

.

Cheers,

swine

Check out Aephid Photokeeper, the powerful digital
photo album solution at www.aephid.com.

Christian Graus3-Nov-02 11:35

3-Nov-02 11:35

Alphablend is known to leak memory, I wrote a replacement, it's availble on the wdj site, sorry I forget when but if you search for my surname, it's the only article of mine that was the feature article ( so the text is online as well as the code ).

Christian

No offense, but I don't really want to encourage the creation of another VB developer. - Larry Antram 22 Oct 2002

Hey, at least Logo had, at it's inception, a mechanical turtle. VB has always lacked even that... - Shog9 04-09-2002

During last 10 years, with invention of VB and similar programming environments, every ill-educated moron became able to develop software. - Alex E. - 12-Sept-2002

Swinefeaster3-Nov-02 21:53

3-Nov-02 21:53

Thanks very much Christian! I found it Smile | :)

. I'm going to try it out and see what I can come up with. Hopefully that will solve most of my problems... Just a few more questions, please...

1. Does AlphaBlend() leak memory on Windows 2000 and Xp as well, or just Windows 98 or Me? (I don't get any crashes on 2000/Xp)

2. I found your article at:
http://www.windevnet.com/documents/s=7628/wdj0109b/

It says "If you download this month’s source code from the WDJ website, you will find an example project, which illustrates the use of these functions and also shows you the steps taken by TransparentBltU(), as shown also in the examples here."
...but unfortunately it which month nor where I can get this example code. Where is that stuff?

Again thanks a lot.

swine

Check out Aephid Photokeeper, the powerful digital
photo album solution at www.aephid.com.

Swinefeaster5-Nov-02 19:19

5-Nov-02 19:19

I've used your code for the Windows 98 implementation, and it fixed the bug! Thanks Smile | :)

.

swine

Check out Aephid Photokeeper, the powerful digital
photo album solution at www.aephid.com.

document filter

tom20003-Nov-02 10:26

tom2000

3-Nov-02 10:26

Hi,

I am a student who doing a project useing MFC. I had creade a single document project. But forget to fill the Document Template Strings, such as the filter name and file extension.

Now I can save and load fuiles but they have not an extension. And when clicks Open, all types of fill is shown.

Can any one tell me whether there is a method can add these functions to a project?

Thanks,
Tom

Re: document filter

Christian Graus3-Nov-02 11:36